The described subject matter relates generally to seals, and more specifically to circumferential seals and seal segments suitable for high temperature environments.
Conventional brush seals for engines, such as axial flow turbine engines, are currently made from low-cost, finely drawn wires derived from basic nickel- or cobalt-based alloys. These conventional brush seal configurations, under the thermal and pressure differentials seen in and around the gas path. At the same time, higher temperature superalloys have been introduced into more parts of such engines to increase efficiency through higher combustion temperatures, which can exceed the creep temperature of conventional brush seal alloys.
Early generations of superalloys are also occasionally used in brush seals. These have relatively low concentrations of gamma-prime precipitate. To date, it has been difficult and impractical to consistently process the more recent generations of superalloys, characterized generally by increased concentrations of gamma-prime precipitate, into the finely sized wires typical of conventional brush seals. Specifically, concentrations of gamma-prime precipitate can be increased to help the material withstand the higher turbine temperatures in advanced gas turbine engines. However, in terms of quality, consistency, and manageable processing costs, it becomes impractical or impossible to process a material having increased concentrations of gamma-prime precipitate into wires having a sufficiently thin diameter for use as a brush seal without unduly sacrificing thermal and mechanical properties of the seal.